In order to interact effectively with the world, people depend on information about the spatial locations of objects in their immediate environment. This information is needed to accurately guide overt movements of the eyes and limbs, as well as covert movements of attention. Because spatial orientation comprises such an integral part of one's daily life, a thorough understanding of the mental and physical processes that underlie it will have important implications for a wide range of behaviors. A detailed model of such behaviors may ultimately facilitate the diagnosis and treatment of movement and attentional disorders, and the design of prosthetic and robotic devices. The research proposed herein is directly concerned with contributing toward such a model. The present project is designed to learn more about the mental mechanisms that underlie the production of eye movements, limb movements, and movements of visual attention. To do this, answers are sought to fundamental questions about such behaviors including: To what extent do eye, hand, and attention movement systems obey similar operating principles or perhaps employ shared mental mechanisms? To what extent do these systems share spatial information? In what coordinate systems and reference frames are the various movements planned and implemented? To answer these questions, three series of experiment are proposed. The first series examines details of eye movements and the extent to which some eye movements may be inhibited by prior movements of visual attention. These experiment will provide new insights into eye movements, visual attention, and the relation between the two. The second series of experiments focuses specifically on eye-hand coordination by examining two phenomena that are known to affect eye movements, and assessing the possible influence of these phenomena on limb movements. Experiments in the third series examine additional questions about the relation between eye movements, hand movements and attention by examining attentional coordinate systems in which movements are planned. Results of the proposed experiments should provide new insights into fundamental processes underlying various aspects of perception, cognition, and action that are relevant to spatially oriented behavior. With these insights, it should be possible to better diagnose, treat, and prevent serious movement and attentional disorders related to mental health.